Who is affected

Stopping having periods after previously having them, known as secondary amenorrhoea, is relatively common - it's estimated to affect around 1 in 25 women at some point in their lives.

It is more common in teenage girls and younger women, and can be much more common in certain groups, such as professional athletes, dancers and gymnasts.

Not starting your periods by the expected age, known as primary amenorrhoea, is much less common. It's estimated to affect 1 in every 300 girls and women.

How absent periods are treated

The treatment for absent periods will depend on the cause.

For example, PCOS can often be controlled using hormonal treatments, and women with hypothalamic amenorrhoea will often start to have regular periods if they cut down on exercise and reach a healthy weight.

In some cases, your doctors may recommend waiting to see if your periods return or start on their own.

Sometimes your periods cannot be restored with treatment, as is usually the case with absent periods caused by premature ovarian failure.

Causes

It is normal for your periods to stop at certain points, although absent periods are sometimes the result of an underlying health problem.

In some cases, a cause may not be found.

Naturally absent periods

It is normal for periods to stop while you are pregnant or breastfeeding, and they often become less frequent during the menopause (when the ovaries stop regularly producing eggs, usually at around 50 years of age).

Becoming pregnant without realising is a surprisingly common cause of an absent period. This often happens when your method of contraception fails without your knowledge.

In the case of pregnancy and breastfeeding, your periods will eventually return. After the menopause, you will stop having periods altogether.

Developmental delays

Girls often start having periods from around 12 years of age. However, some girls don't have their first period until later, particularly if this was the case with their mother or older sisters.

This is usually nothing to worry about, as most of these girls will eventually start having periods by the time they are 16-18 years old.

Contraception

Some women who use a contraceptive implant (such as a Mirena coil), a contraceptive injection or, less commonly, the contraceptive pill (sometimes called the 'mini pill') may find their periods become irregular or stop completely.

Your periods should start again once you stop using these forms of contraception, although occasionally these effects can persist.

If you have not been using these types of contraception for six months or more and still have not had your period, contact your doctor for advice.

Medical conditions

There are also medical conditions that can cause absent periods. Depending on when these conditions develop, they can mean a girl doesn't start having periods by the expected age (primary amenorrhoea), or a girl or women who has previously had periods stops having them (secondary amenorrhoea).

Some of the main medical conditions that can cause absent periods are described below.

As well as causing absent periods, other symptoms of PCOS include excessive body hair, problems getting pregnant and weight gain.

Hypothalamic amenorrhoea

The menstrual cycle is regulated by part of the brain known as the hypothalamus. This produces hormones that cause the ovaries to release eggs. In cases of hypothalamic amenorrhoea, the hypothalamus stops producing these hormones and the menstrual cycle stops.

Exactly why the hypothalamus does this is unclear, but it has been linked to:

excessive weight loss, for example, due an eating disorder such as anorexia nervosa

Hypothalamic amenorrhoea is more common in women whose profession requires a combination of physical fitness and maintaining a low body weight, such as athletes and dancers.

Even if you are not concerned about not having a period, you should still seek medical advice if you think you have hypothalamic amenorrhoea, as it can lead to brittle bones (osteoporosis) and put you at risk of a bone fracture.

Hyperprolactinaemia

Hyperprolactinaemia means you have excessively high levels of a hormone called prolactin in your body.

High levels of prolactin are normally only required after you have given birth, as they help stimulate production of breast milk. Having high levels at other times can disrupt the normal menstrual cycle and lead to absent periods.

Hyperprolactinaemia is thought to affect around 1 in every 200 women and can have a wide range of causes, such as:

Women who regularly use heroin also often develop hyperprolactinaemia.

Premature ovarian failure

Premature ovarian failure is when the ovaries stop producing eggs in women who should still be young enough to ovulate (usually 45 or younger).

It is estimated that premature ovarian failure affects 1 in every 100 women before the age of 40 and 1 in every 20 women before the age of 45.

It is thought many cases of premature ovarian failure are caused by the immune system malfunctioning and attacking the ovaries. The condition has also been linked to having chemotherapy or radiotherapy.

You should seek medical advice if you suspect you have premature ovarian failure, even if you are not concerned about having periods. This is because having this condition can put you at risk of osteoporosis and heart disease.

Thyroid conditions

The thyroid gland is found in the neck. It produces hormones that are released into the bloodstream to control the body's growth and metabolism. They affect processes such as heart rate and body temperature, and help convert food into energy to keep the body going.

In some women, the thyroid gland can:

produce too much thyroid hormone – this is known as having an overactive thyroid gland or hyperthyroidism

produce too little thyroid hormone – this is known as having an underactive thyroid gland or hypothyroidism

Both hyperthyroidism and hypothyroidism can cause absent periods.

Genetic conditions

Although uncommon, absent periods can also be caused by a number of conditions caused by problems in your genes. These include:

Turner syndrome – a condition affecting around 1 in every 2,000 girls, which causes those affected to be born with ovaries that do not produce the hormones required to trigger the menstrual cycle

Kallmann syndrome – a rare condition affecting around 1 in every 10,000 births, where hormones that normally trigger sexual development are missing

androgen insensitivity syndrome – a rare condition affecting around 1 in every 20,000 births, where a child is genetically male but their genitals can appear to be female

Birth defects

In rare cases, absent periods may be caused by a problem in the development of a girl's reproductive system that has been present from birth, such as having no womb or vagina.

Diagnosis

You should see your doctor if you are worried about problems with your periods so they can identify the cause.

Your doctor will usually recommend a pregnancy test because pregnancy is the most common cause of absent periods and can occur unexpectedly if the method of contraception you use fails without you realising.

Your doctor will also note your medical history, your family's medical history, your sexual history, any emotional issues you are having and any changes in your body weight.

They will also assess whether you are going through the normal physical stages of puberty.

Seeing a specialist

Depending on what your doctor thinks may be the cause of your absent periods, you may be referred to either a gynaecologist (a specialist in treating conditions that affect the female reproductive system) or an endocrinologist (a specialist in treating hormonal conditions) for further investigation and any necessary treatment.

Your specialist may give you a full gynaecological examination and carry out various tests, including:

blood tests to see if you have abnormal levels of certain hormones, such as prolactin, thyroid-stimulating hormone, follicle-stimulating hormone or luteinising hormone

You may be referred to a dietitian if you are underweight (a body mass index of less than 18.5) or obese (a body mass index of 30 or more), or to a psychiatrist or psychologist if your doctor thinks you have an eating disorder.

Treatment

The treatment for absent periods depends on what is thought to be causing the condition.

In some cases, a "wait and see" approach may be adopted in case your periods start or return by themselves. This approach is most often used for girls who have not yet started their periods, because in many of these cases periods will start naturally by 18 years of age.

If tests suggest an underlying medical condition is causing your absent periods, treatment will depend on the specific condition. It is sometimes possible to be treated by your doctor, although some treatments are only available from specialists.

Hypothalamic amenorrhoea

Hypothalamic amenorrhoea is absence of periods caused by things such as extreme weight loss, excessive exercise, stress and long-term (chronic) conditions. It can be treated by addressing the underlying cause.

If your symptoms are the result of excessive weight loss, you may be referred to a dietitian, who can advise on safe ways of regaining a healthy weight.

If your weight loss is the result of an eating disorder, such as anorexia, you will need to be referred to a psychiatrist (a doctor who specialises in treating mental health conditions) who has experience in treating eating disorders. Read more about treating anorexia nervosa.

If your symptoms are the result of excessive exercise, you will be advised to reduce your levels of physical activity. If you are a professional athlete or similar, you may benefit from a referral to a doctor who specialises in sports medicine. They should be able to advise about how you can maintain fitness and physical performance without disrupting your periods.

If your symptoms are the result of stress, a type of talking therapy called cognitive behavioural therapy (CBT) might help. CBT is a type of therapy that aims to help you manage your problems by changing how you think and act.

If your symptoms are the result of a long-term underlying health condition, treating this illness may help restore your periods. For example, if you have type 1 diabetes, you may need regular injections of insulin.

Hyperprolactinaemia

The treatment for hyperprolactinaemia (where a person has abnormally high levels of a hormone called prolactin) will depend on the underlying cause.

For example, if hyperprolactinaemia is the result of a brain tumour, surgery, radiotherapy or chemotherapy may be required to remove or shrink the tumour. If hyperprolactinaemia occurs as a side effect of a medicine, your medication may need to be reviewed.

Premature ovarian failure

If you have premature ovarian failure (when the ovaries stop producing eggs in women who should still be young enough to ovulate), you will usually be treated with hormone medication.

These treatments can help reduce your risk of complications associated with premature ovarian failure, such as osteoporosis (weakening of the bones), but they will not necessarily restore your periods.

Thyroid conditions

Treatment options for an overactive thyroid gland include thionamide medication, which helps reduce thyroid activity, and a type of radiotherapy called radioiodine treatment, which can be used to reduce the size of the thyroid gland.

Treatment options for an underactive thyroid gland include a medication called levothyroxine, which can stimulate thyroid activity.